1. Field of the Invention
The present invention relates to an engaging member of a fastening device made of synthetic resin which substitutes for a conventional snap button and ordinary button.
2. Description of the Related Art
A conventional engaging member of a fastening device of this kind made of synthetic resin has been disclosed in, for example, Japanese Patent Application Laid-Open No.9-75113. This Laid-Open invention was proposed by the same inventor of the present invention and as for an outline structure of that invention, each ends of two flat plate portions substantially parallel to each other and made of thermoplastic synthetic resin having the same shape are connected integrally with a connecting portion in a substantially U-shaped section. A number of engaging elements are formed in an upright position on the surface of one of the flat plate portions connected with the connecting portion. Additionally, a tab is integrally molded of the same resin material on the connecting portion so as to project outward in parallel to the flat plate portions from the connecting portion. Further, groove-like sewing lines are formed on the surface of each of the flat plate portions along an entire peripheral edge thereof.
Because this engaging member of the fastening device is an integrally molded product of thermoplastic synthetic resin, not only its configuration is stable. but also a fashionable product having a desired configuration and pattern can be produced through a single molding process at a low cost. Particularly because this engaging member of the fastening device is molded in a condition in which first and second flat plate portions are maintained in parallel and connected with the connecting portion, the engaging member of the fastening device can be attached to clothes neatly, and positioning of the engaging member of the fastening device is easy. Further, because the tab is integrally molded on the engaging member of the fastening device to project outward from the connecting portion, an operation for opening and closing the engaging member of the fastening device is also easy.
However, although of each of the flat plate portions needs to be molded as thin as possible to ensure flexibility of the clothes on which this engaging member of the fastening device is attached, a thinner sewing line is formed along an entire peripheral edge thereof as described above, and therefore, the engaging member of the fastening device is likely to be broken at that portion, which means there is a limit in reducing the thickness of the flat plate portion. Further, as the thickness thereof decreases, it is more difficult to make outlines of the respective flat plate portions correspond to each other when the two flat plate portions are set up on an edge of clothes, so that the aforementioned sewing lines formed on both the flat plate portions often displace from each other. Therefore, it is difficult to sew the engaging member of the fastening device accurately along the same sewing line.
Even if the thickness of each flat plate portion is minimized to cope with such a disadvantage, when the engaging member of the fastening device is attached to an edge of clothes, it comes that an edge of the clothes is nipped by two flat plate portions at the mounting portion, so that the portion feels extremely stiff. Although there is no problem in closing the engaging member of the fastening device because it only has to be pressed, particularly upon opening it, unless the opening operation is carried out with a mating female fastening device member being pressed until the opening is finished, the whole engaged portion moves so that it is impossible to make a smooth opening operation. Therefore, upon attaching/detaching the surface engaging member of the fastening device, particularly upon detaching it, it is difficult to detach the entire engaging member of the fastening device all at once, but instead it must be detached with one fastening device member being rolled up, which is a typical attaching/detaching operation for a surface fastener.
Further, because the flat plate portion facing the surface of the clothes is sewed along an entire peripheral edge thereof, at the time of the opening operation described above, a shearing force is applied to a sewing yarn sewn perpendicular to the direction of the opening operation, so that the sewing yarn may sometimes be torn by repeated opening operations.
What is most difficult to handle of this engaging member of the fastening device is that because the two flat plate portions are of the same shape in a plan view, when this is attached to an edge of the mounting portion of the clothes, the two flat plate portions must be turned outward with respect to the connecting portion so as to open the end portion thereof and then an edge of the mounting portion of the clothes is inserted into this opening. Such a troublesome procedure is needed to attach the engaging member of the fastening device to the clothes.